Screw rod pitch changing device

The utility model discloses a screw rod pitch changing device, which relates to the technical field of processing tools, and adopts the technical scheme that the screw rod pitch changing device comprises a working table, a first bearing seat, a second bearing seat, a third bearing seat and a fourth bearing seat are respectively and fixedly arranged at the top of the working table, a motor is fixedly arranged at the top of the working table, and the output end of the motor is fixedly connected with a second coupler; a long screw rod is fixedly arranged on one side of the second coupler, penetrates through the fourth bearing seat and the third bearing seat and is connected with the fourth bearing seat and the third bearing seat through bearings, a first coupler is installed at one end of the long screw rod, a short screw rod is installed on one side of the first coupler, and the end, away from the first coupler, of the short screw rod is connected with the first bearing seat through a bearing. The short screw r